Although the opponents of the 2015 Iranian nuclear deal often speak of Tehran in hyperbolic terms—as a "murderous regime[1]" and as an exporter of “death and destruction[2]”—their main criticism of the agreement is more mundane. It revolves around clauses known as the “sunset provisions,” which stipulate when the various restrictions imposed on Iran’s nuclear program expire and which critics say provide Iran with a patient pathway[3] to acquiring nuclear weapons.

On September 19, Israeli Prime Minister Benjamin Netanyahu, one of the staunchest critics of the deal, which is known officially as the Joint Comprehensive Plan of Action (JCPOA), rebuked it yet again[4] at a meeting of the United Nations General Assembly. “In a few years, [nuclear] restrictions will be automatically removed,” he said, “not by a change in Iran’s behavior, not by a lessening of its terror or its aggression—they’ll just be removed by a mere change in the calendar.” U.S. Secretary of State Rex Tillerson, although not known as the most hawkish on this issue in Donald Trump’s White House, echoed the same view later that day, saying[5], “The [deal’s] most glaring flaw is the sunset provision…We all know that this is merely a kick-the-can-down-the-road agreement.”

What Netanyahu, Tillerson, and other critics take issue with is not just that these expiration dates arrive too soon, but that there are expiration dates at all. Some of the deal’s prohibitions, such as on the number of Iran’s first-generation centrifuges and on the research and development of more advanced ones, are set to end in 2025, but Iran’s total enrichment capacity (less than a third of what it was prior to the deal) will remain where it is now until 2028, thanks to limits on Iran’s ability to enhance and deploy advanced centrifuges.

Other key limitations last even longer. Until 2030, the level of enrichment is restricted to 3.67 percent—far below the 90 percent needed for weapons-grade uranium. The path to a plutonium weapon is